Evaluation of novel live and inactivated Salmonella - Vectored vaccines for immunization of chicks in-ovo and at hatch

As we previously reported, an attenuated DeltaaroA/Delta htrA Salmonella enteritidis strain (DeltaSE ) expressing two M2e epitopes and an abbreviated CD154 sequence on the bacterial cell surface provided high, persistent, and neutralizing antibody titers against several influenza serotypes when administered post-hatch. The present studies evaluate in ovo administration of DeltaSE on hatchability and antibody production. In addition, clearance of DeltaSE from liver, spleen, and cecal tonsils was evaluated. At day 18E chicken embryos were vaccinated with 0.25 mL of 3.25 x 103, 2.5 x 105, and 2.7 x 105 cfu DeltaSE/embryo (air cell) in experiments 1, 2, and 3, respectively. Control groups were injected with 0.25 mL sterile saline. Chicken hatchability was not affected in these experiments and no clinical signs of disease were detected in any experiment. Liver, spleen, and cecal tonsils were aseptically removed from chicks and cultured for DeltaSE recovery. Serum M2e- and DeltaSE-specific IgG antibody response was measured at specific sampling periods for each experiment. Serological levels for IgG anti-M2e antibodies increased during the first week of age. However, IgG anti-DeltaSE antibodies were not detected at any of the sampling times. Clearance of DeltaSE from liver and spleen and cecal tonsils was greatly diminished by the end of each experiment. Although a brief immune response was observed at 1 week post-vaccination, no antibody against M2e was observed at later times. These data suggest that in ovo administration of this vectored M2e-based vaccine is not a potentially effective means of prophylaxis in commercial poultry.;The objective of the subsequent studies were to evaluate the effect of an inactivated a Salmonella enteritidis recombinant vaccine (DeltaSE) expressing surface type A influenza M2e epitopes on the immune response of broiler chickens. Treatment groups consisted of heat- (1 hour at 65°C) or formaldehyde- (0.05%) inactivation (10 7 cfu/mL) alone or in combination with an adjuvant (aluminum hydroxide; 1 or 2.6 mg/dose) and were evaluated by ELISA for antibody against DeltaSE or M2e. In Experiments 1 and 2, day-of-hatch broilers were divided into groups (n=50), neck tagged, placed in a common pen, and injected with 0.2 mL saline (control), or heat- or formaldehyde-inactivated recombinant bacteria with or without adjuvant at day-of-hatch, and with or without booster vaccination at day 21 post-hatch. Blood samples were collected and body weights were measured at approximately 10 day intervals in both experiments. No effect on performance was observed, and anti-M2e responses were not significant between groups at any age, although significantly p< 0.05 increased antibodies against DeltaSE was observed Although previous studies have indicated that live DeltaSE inoculation in day-of-hatch chicks results in marked increase in M2e antibody levels, the present study indicates that parenteral administration of this vectored vaccine is unlikely to provide protective immune response against avian influenza when inactivated or adjuvated by these methods.